[Amps] What to do with tubeless sweep tube FL2000 ?

[donii at sympatico.ca]

I've just gotten this nearly mint and hardly used FL2000 for a song. The 
original 6KD6's are nearly new but I would like to keep them for my 
great FT-501 with CW filter and very tired finals. Is there some type of 
conversion the FL2000  can undergo with another type of tube(s)? It 
would be a pity just to gut it because I stole it's tubes!  Am I barking 
up the wrong tree? Maybe I should retube the FT-501 and use the FL2000??
The FL2000's  power supply gives 1200 volts dc. and I can do moderate 
circuit modifications to accomadate one or more tubes. Maybe put a 
doubler circuit in the H.V. bringing it up to 2400 v. then I could put 
in 572's or something else?
Another question: Are the four original 6KD6's in the FL2000 matched ?
73's all
VE2FAR